Improvement in instruments for drawing geometrical lines



WILLIAM RI'I'CIIIE, OF WILMINGTON, ILLINOIS.

x Letters Patent No. 100,072, dated February 22, 1870.

IMPROVEMENT IN INSTRUMENTS PQR DRAWING GEI-OMETRICAL LINES.

The Schedule referred to in these Letters Patent and making part of the same.

To all whom t may concern Be it known that I, WILLIAM RITcHIn, of .Wih mington, in the county of llill, and State of Illinois, have invented a new and improved Instrument for Drawing Geometrical Lines; and I do hereby declare that the `following is a full, clear, and exact description thereof, which will enable others skilled iu the art to make and use the saine, reference being had to the accompanying drawings forming part of this specification, in which- Figure 1 representsa plan or top view of my improved instrument for drawing geometrical lines, showing it adapted to Vthe production of parallel and radial straight lines and of regular circles.

Figure 2 is a side elevation of the same. ff 1 `igure 3 is a plan or top view of the grooved tranimel-bed used in connection with the saine.

Figure 4 is a plan or top view of the trainmel-slide and bedl l Figure 5 is an inverted plan view of the trainmelslide.

Figure 6 is aside view o the pencil-tube.

Figure 7 is a plan or top view of the same.

Figure 8 is a plan or -top view of the instrument, showing it adaptel'l to the production of spiral and eccentric curves around a liked center.

.Figure 9 is a plan or top view ot' the same, showing it adapted to the production of volutes around an oval, and also the ovals.

Figure 10 is a plan or 'top view of the center block.

Similar letters of reference indicate corresponding parts.

This invention relates to a new instrument which can be used for producing'all kinds of cnrvesas well as straight lines, and which can he readily set and adjusted to .draw with exactness the requisite curve or line.

The invention consists chiefly in the arrangement of a frame which carries a pencil or other marking instrument, and which is supportedon a revolving frame or bed, wherein it can also slide.

The combined sliding and revolving inotio'n of the instrument produces the volutes, the grades of which can berregnlated by the angle at which the instrument is caused to slide. The invention also consists in the general combination of devices used on the instrument with a tram- 'mel for producing ovals and volutes around the saine. 4

A in the drawing represents a bar made of wood or other suitable material, provided at one end with a roller, B, whose diameter is such that it holds the bar about half an inch above qthe level on which the rpller rests.

C is an arm projecting at right angles from the'bar A, near to the end on which the roller B is attached.

The-outer end of the arm C is supported by a caster-wheel, D, as shown.-

The bar A is slotted longitudinally, as shown, and is provided with an extension piece or slide, E, which 'is a bar secured by screws a, a to the under sideof the bar A, and longitudinally adjustable thereon.

To the inner end of the slide E is pivoted, by a pin,

l), a rod or'center arm, F, which works on the under.

side of the slide E, so that it may be swung entirely under the same, as by dotted lines in iig. 1,01' at right angles thereto, as by full lines in the same figy ure, or at any suitable intermediate angle.

The outer end of the center arm works on a graduated arc, G, which projects from the outer end of the slide E, and to-which the arm can be clamped by a suitable screw, cin any desiredposition.

Between the inner end of the slide E and the arm C is arranged, in or on the bar A, aveitical tube, d, for the recept-ion ot' a pencil, H. This -tube may either be ttcd through the bar A, as-in iig. 1, or it may be secured to the side of the same by-means of projecting ears e and screws f, as in 6 and 7.

lhe pencil H should be weighted at its upper end to make the required marks without requiring additional pressure.

I represents a block of suitable length, grooved lon- Vgitudinally at its upper face, and provided with one or more friction-rollers g at the bottom of the groove` At one end projects from the block I an ear, l1, which has a small aperture to receive a pin, fi, by whichtlle block can be 'pivoted to a drawing-board. At .the opposite end, the block is supported by one or more rollers jj.

The center arln F is, aft-er the block has been pivoted to the board, placed into the groove of the same as shown, and can readily slide therein, as the frictionroller facilitates the motion.

The block can readily revolve on the pin i.

It' the center arm should be locked to 'the block, the pencil would, when the device was set in motion, describe a regular circle around the pin t, as no other motion of either part is then possible. As, however, the center arm ts loose into the groove of the block, and can easily slide therein, the motion produced will be entirely dii'erent, provided thev cent-er arm be clamped to the arc,`in,'a position between the two shown in fig. 1.

The roller B willl have th'e tgendency to revolve in a straight line, while the rotation imparted tothe frame forces it to revolve on the pin i. The two4 motions lthus combined will produce a component movement,

recorded by the pencil in form of a spiral line or-volute around the circle.

by the angle at v revolves on the pin t'.

A, Fig. 8 clearly shows the position of the instrument and several curves described by it.

Into the pivoted end ofthe block I is fitted a screw, K', which can be moved in or out, and which with its head strikes against the downward-projecting pivot b, to thereby regulate the diameter of the circle around which the volute is described.

When the` screw K strikes the pivot b, the centerarm canY slide no further inward, and thereby the fnr. ther revolution of the instrument will describe a reg ular circle around the pin i.

Instead of the block I and the center pin i a double grooved tramniel-bed, J, carrying a trammel-slide, L,

Ywith. two pins l l, may be employed, the slide having its upper surface grooved similar to the block'I.

The trammel-bed is by two pins secured to the drawing-board, and the center arm tted into the groove of the slide.

The motion of the instrument on thetrammel-bed will produce ovals and volutes thereto, as indicated in iig. 9.

When the instrument is placed upon the block I,

and the center arm set at right angles to the bar A,

the device may be moved longitudinally in the groove of the block to produce parallel lines m m, the distances between which are regulated by the extension of the lever A on the slide E.

When the center arm is folded directly under the slide, so that the block I will also be under the slide and bar A, ,radial lines 'n n c an be drawn by gradually turning the block and sliding the center arm in and out without turning the instrument.

AThe grooved block, being pivoted to the drawingboard, will revolve on the pivot, describing a true circle, whether there are wheels on` it or not. The

l' wheels are placed there merely to reduce friction on the drawing-board, and the wheel within the groove Of the block is simply to reduce the friction that would ensue from the center arm sliding on the ,bed Of the groove.

If the center arm ofthe instrument is placediin the grooved block, it forms a radius, of which the roller B` is the tangent and the pivot of the grooved block is the center.

If the tangent and radius are at right angles, and the instrument is pushed forward, the center arm, being retained in position by the edges of thegroove, forms a connected lever, with which the instrument revolveson the pivot, making a true circle.

If the roller B and the bar A are at right angles, and the bar A and the center arm are at right angles, the roller B and :the center arm will be parallel, and

Vbeing pushed, as above stated, there being now no obstruction to the center arm, the instrument will describe a straight line until the pivot of the slide cornes in contact with the bed-screw of the grooved block, when it willjmake a circle.

If the center arm and the roller B be fixed at an angle of forty-five degrees and pushed, as above, the friction being light and the roller B being heavy, it is not effected bythe friction, but pursues its path at the same angle, and causes the center arm to slide through the grooved block while revolving, and recording a true volute of forty-five degrees. The roller' B does not slip, its variations-being caused by simply changing the plane Of its motion.

The following is the rulev to Obtain a volute of a given character, the diameter of the eye and the ex-` treme outer point of the volute from the center being given, with the angle at which the curve shall deviate from a straight line:

Adjust the instrument by fastening the slide so that the distance between the center of the pivot, which fastens the center arm with the slide, and the center of the pencil-tube shall ce one-half the diameter of the eye required, fasten the center arm to the graduated arc at the required angle, and place the pencil in the pencil-tube at the required distance frtmi,

`the center, and move the instrument, as above, until the pivots of the grooved block and center armare perpendicular. Any outer or intermediate lines verging to the same center, are formed by 'simply taking another point of commencement with the pencil, with out altering the adjustment of the instrument.

Where parallel lines are required, fasten the slide so that the distance between the end of it and the pencil-tube shall be the distance required between the lines. Describe the Out-cr line first until a Vpoint is arrived at where the radial distance between it and the adjoining curve is equal to that required, then remove the peni-il and shift the slide close up to the v pencil-tubeand describe. Any intermediate lines are. formed by securing the, slide to the arm ofthe instrument at a distance from the pencil-tube equal to the distance between the inside line and the required line.

Havingthus described my invention,

I claim as new and desire to secure by Letters Patent- 1. The combination, with each other, of the bar A, roller B, pivoted4 center arm F, and arc G, all arranged as described,'to constitute a drawing-instrument, as specified.A

2. The grooved block I pivoted to the drawingboard and adapted to receive the cent-er arm/IE` of the drawing instrumentas set forth.

3. The combination of the grooved trammel-arm and friction-wheel with the center, `each of said part-s being constructed and arranged as and for the purpose specified.

. WM. RITGHIE.

Witnesses:

J OHN CAMPBELL, JOHN O. THOMSON. 

